It wasn't too long ago that vinyl windows were considered a less-than-ideal choice for replacement windows. But advances in design plus improvements in the formulation of polyvinyl chloride (PVC) have made vinyl windows a high-quality product that competes favorably with wood.

Vinyl windows have always had some advantages over aluminum and steel. Metal is a highly efficient heat conductor-a great property when it comes to pots and pans, but not so slick when you're talking about window frames. As window glazing has improved, the difference in insulating value between the glass and the frame of a metal window became greater and greater.

PVC, on the other hand, is a nonconductor of heat. It doesn't truly insulate like wood, but the design of a vinyl window adds greatly to the frame's insulating value. The primary reason that insulating glass works is because there is a pocket of trapped air, called dead air space, between the inner and outer panes. Vinyl window frames work on the same principle. The frames are hollow, built with multiple chambers to add strength (see image). Those chambers also trap air and thereby slow heat transfer.

Good quality vinyl windows are nearly equal to wood windows in their overall insulating value, but not just because of the frames. Compared to old shop-built wood double-hung windows, the factory weatherstripping in modern vinyl windows allows only a fraction of the air leakage around the sash. As a rule, air infiltration is even more important than insulating quality in preventing heat loss.

Vinyl windows come in a variety of styles, including single- and double-hung (see image above), horizontal sliding (see image), casement, awning and hopper. Sliding patio doors are also available. The color is part of the PVC formula, so vinyl windows never have to be painted. Most come in white and almond, some with woodgrain overlays inside.

Vinyl windows offer the same style features found on other top-quality windows-divided light grids, decorative glass, tilt-out sash on single- and double-hung units, high-efficiency locking systems, premium configurations such as circle tops, bay and bow units and even brass hardware. Like all vinyl products, they are also maintenance-free.

A few manufacturers still make dark brown windows, but many have stopped manufacturing dark colors. Despite advances in formulation, vinyl is still more sensitive to temperature variations than other window materials, and dark colors absorb heat more readily than light colors.

FEATURES OF VINYL WINDOWS

There are differences in the quality of vinyl windows just as there are in any building product. Some of the features that distinguish different windows include:

Vinyl formulation. Early vinyl windows had problems with extreme expansion and contraction during temperature swings, as well as fading, peeling and cracking when exposed to direct sunlight. Manufacturers have switched to PVC without plasticizers (called UPVC) to minimize movement and developed additives that help resist the ultraviolet rays in sunlight.

Frame design. Vinyl window frames may be screwed together like aluminum windows, or welded at the corners. Windows with welded frames tend to be sturdier, as well as more energy efficient, since air is sealed inside.

Glazing. Modern vinyl windows are available with the same high-tech glazing used in top-of-the-line wood windows-insulating glass with low emissivity (low E) coatings (see image), and filled with argon gas to increase insulating value.

Many states have adopted an energy efficiency rating system for windows developed by the National Fenestration Ratings Council (NFRC). The NFRC rating lists the U-value for the overall window, not just the glass. The lower the U-value, the more energy efficient the window.

If your house has older wood double-hung windows, vinyl is a good replacement choice and a reasonably easy do-it-yourself project. You don't have to remove your old windows entirely, because vinyl replacement windows are made to fit in the sash opening.

MEASURING VINYL WINDOWS

The most important part of the installation procedure comes before you even have your windows. It is critical that you measure your old window opening properly and accurately (see image).

Vinyl windows are custom-built and can't be returned if they don't fit. Most are manufactured in 1/4" increments, and you'll want to get the closest fit possible.

Manufacturers' measuring instructions vary, but the following procedures are typical.

To measure the width, raise the lower sash and measure the jamb-to-jamb width in three places-near the top of the window, at the middle and close to the bottom.

To measure the height, measure from the head jamb to the sloped sill just past where it meets the inside window stool.

Don't assume that all your windows are the same size. Draw a rough sketch of your house and number each window you plan to replace, then measure each of them separately.

INSTALLING VINYL WINDOWS

To install a vinyl replacement window, first remove the old sash. A traditional double-hung window has two sets of removable stops (see image). All have an inside stop that holds the lower (inner) sash in place and a blind stop that separates the two sashes. The outside stop is nailed to the edge of the sash and is not removable.

Pry off the inside stops carefully so you can reuse them. Cut the sash ropes and remove the lower sash, then pry out the blind stop and remove it. Remove the upper sash.

Set the replacement window in the opening. It should fit snugly between the stool on the inside and the outside stops of the old window on the outside (see image). If the new window is narrower, you may need to nail a strip of wood to the jamb to fill the gap between the window and the outside stop.

Some vinyl replacement windows have sloped extrusions on the bottom that match the sloped sill of your old window (see first image below); others are flat. If the bottom of your new window is flat, you may be able to use a piece of lattice or door stop as a support for the front edge of the window (see second image below).

If not, you'll have to rip an angled support. To do so, set the window in place in the opening, and measure the gap between the front lower edge of the window and the old sloped sill.

You can make supports for all your windows at one time. Plane the edge of a board at an angle that roughly matches the slope of the sill, then rip a strip of wood to match the gap. To install the support strip, cut it to length and nail it in place directly beneath the point where the front edge of the new window will rest.

Center the window in the opening. Use a carpenter's square to make sure the window is square, then shim the sides of the window directly behind the predrilled screw holes in the jamb. Screw the window in place through the side jambs, then replace the inside stop.

Go inside and check the window to make sure it operates properly. Then go back outside and run a narrow bead of caulking all around the window to seal the gap at the outside stop.

Check your state and local codes before starting any project. Follow all safety precautions.
Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and
associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any
contributor nor the retailer can be held responsible for damages or injuries resulting from the use of
the information in this document.

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